I have removed lots of broken bolts and screws from metal and wood but now have an impasse, and I will need machinist help. There are six M8 stainless bolts imbedded in a thin aluminum water jacket of a disassembled cylinder-case. Heat and strong force will ruin the case. A suggestion was to dissolve the bolt using nitric acid, I do not know about that process. A sailor friendly machine shop ( with an EDM machine ) not far from Bosston/Providence or in New England would be helpful info. Anyone?

I had a similar problem and managed to drill out enough of the center of the bolts to collapse them inward with a small punch then extract the hollow remnants. I started very carefully with a small diameter bit then continued to remove material from the center by increasing the drill size.

Drill out almost completely, then using a pick/scribe peel the bolt remains from the corro-thread area, is my fallback plan. Sharp aim of the center and luck might work out. The stainless seems extra tough, will not readily collapse, and the corrosion itself seems very hard. Acid is a mystery to me and seems far-fetched. Machine work might be too costly. I might drill, grind and pick at the remains.

Take it to an auto shop with a MIG welder. Have them weld a 10mm nut on the end of the broken stud and immediately put an impact on it and spin it out. They should put the nut over the stud and weld through the hole. Fill it up. The weld won't stick to the aluminum but the heat will break the corrosion and allow the piece to come out. It might take a couple tries.
I was a Porsche mechanic. How many broken exhaust studs do you suppose that I've removed from aluminum and magnesium?
About $10,000.00 worth of profits over the years on this method, that's how many.

center drilling and collapsing STAINLESS bolts without damaging the softer aluminum around it is going to be tough for a DIY job.

Some pics would be a big help-

Sorry, I have no pics. It was a tedious process. I was removing ss machine screw stubs from my pedestal on the mooring with a hand held drill. I managed. Swearing at the dopes who don't understand "No Wake", helped. The ss I was dealing with may not have been as hard as the bolts you are removing. You should be able to jig up in a drill press. My "small punch" was an awl.

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